<!DOCTYPE html>
<html lang="zh-CN">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>画板</title>
    <link rel="stylesheet" href="style.css">
</head>

<body>

    <!-- <div id="canvas">

    </div>
    <script>
        canvas.onmousemove = (e) =>{
            // console.log(e)
            // console.log(e.clientX)
            // console.log(e.clientY)
            let div = document.createElement('div')
            div.style.position = 'absolute'
            div.style.left=e.clientX + 'px'
            div.style.top=e.clientY+'px'
            div.style.border = '1px solid red'
            div.style.width = '20px'
            div.style.height = '20px'
            div.style.borderRadius='50%'
            div.style.marginLeft='-10px'
            div.style.marginTop='-10px'
            div.style.background='black'
            canvas.appendChild(div)
        } 
     </script>-->
    <canvas id="canvas" width="100" height="100"></canvas>
    <script>

        let canvas = document.getElementById("canvas");
        canvas.width = document.documentElement.clientWidth
        canvas.height = document.documentElement.clientHeight
        let ctx = canvas.getContext("2d");
        ctx.fillStyle = "black";
        ctx.strokeStyle = "none";
        ctx.lineWidth = 5;
        ctx.lineCap="round";//使线条变得圆滑
        function drawLine(x1,y1,x2,y2){
            ctx.beginPath();
            ctx.moveTo(x1,y1);
            ctx.lineTo(x2,y2);
            ctx.stroke();
        }

        // drawLine(0,0,500,500);
        let painting = false
        let last
        var isTouchDevice = 'ontouchstart' in document.documentElement;
        
        if (isTouchDevice) {//手机端
            canvas.ontouchstart = (e) =>{
                let x = e.touches[0].clientX
                let y = e.touches[0].clientY 
                last = [x,y]
            }
            canvas.ontouchmove = (e) => {
                // let x = console.log(e.touches[0].clientX)
                // let y = console.log(e.touches[0].clientY)
                // console.log(x, y)

                let x = e.touches[0].clientX
                let y = e.touches[0].clientY
                drawLine(last[0],last[1],x,y)
                last = [x,y]

            }
        } else {//PC端
            canvas.onmousedown = (e) => {
                painting = true
                last = [e.clientX,e.clientY]
            }
            canvas.onmousemove = (e) => {
                if (painting === true) {
                    // ctx.fillRect(e.clientX -5,e.clientY -5,10,10);画方形
                    //画圆
                    drawLine(last[0],last[1],e.clientX,e.clientY)
                    last = [e.clientX,e.clientY]
                } else {
                    console.log("什么都不做")
                }
            }
            canvas.onmouseup = () => {
                painting = false
            }
        }


    </script>

</body>

</html>